(Immunoassay for Polynucleated Aromatic Hydrocarbons in Soil and Water)

Certification No: 96-01-022

Technology Description:

The technology is based on the principle of enzyme-linked immunosorbent assay (ELISA); the polyclonal antibodies are bound to micron-sized superparamagnetic particles. Water samples are tested directly; soil samples are extracted with a modified methanol solution using the Ohmicron RaPID Prep PAHs Sample Extraction Kit and diluted prior to assay. After reaction and removal of excess reagents, and enzyme-mediated reaction is initiated and the intensity of the resulting blue color determined in a portable field or a laboratory photometer.

While the individual PAHs respond differently to the assay, contamination of the soil is indicated in terms of a manufacturer-supplied calibration standard which contains phenanthrene. The assay responds with different sensitivities to a number of PAHs, including several known carcinogens. Three concentration levels of calibrator are provided with the test kit.

The assay is semi-quantitative in that it is intended for the detection and quantification of PAHs in terms of the supplied calibrator levels. The normal testing range in water is from 0.93 to 66.5 ppb as phenanthrene. Samples containing gross particulates should be filtered. The assay sensitivity in oil is 0.25 ppm. High concentrations does not respond to lower aromatic hydrocarbons including naphthalene. Humic acids are a known possible interfering agent. Not all matrix effect may yet be known, and confirmatory analysis by approved methods, such as U.S. EPA Method, is necessary to identify and quantify individual PAH compounds, the confirm positive results in site characterizations, and to decide on-site closure after cleanup.

Soils with up to 20 to 20 percent water content can be tested; extraction is reduced at soil water content over 30 percent. As with similar assays, certain temperature controls are required for reagent storage and for carrying out the assay. The assay should be used only by trained individuals to reduce operator-caused variability.